if you mean supply and demand, then
supply: how much of something you have
demand: how much people want it
so if the supply is high (there are alot of product) and demand is low (not many people want it), then the prices are usually low, but
exg gassoline
so there is a limited supply in the world so the supply is low, but the demand is high (many people need gas) so the prices are high
so gas is on of them